Chemical relaxation of cetylpyridinium iodide micelles in high electric fields
1975; Elsevier BV; Volume: 53; Issue: 2 Linguagem: Inglês
10.1016/0021-9797(75)90015-6
ISSN1095-7103
Autores Tópico(s)Thermodynamic properties of mixtures
ResumoThe electric field jump relaxation technique has been applied to cetylpyridinium iodide above but close to the critical micelle concentration. On monitoring the intrinsic optical absorption of the charge transfer band three chemical relaxtaion processes are observed in the range 10−8 to 10−3 sec: An increase of the field strength causes a fast dissociation (τ ≈ 50 μsec), an association (τ ≈ 1 μsec), and a slow dissociation (τ ≈ 50 μsec). The fast dissociation effect represents the relaxation of the counterion binding. The kinetic constants for the bimolecular reaction are kR = 1.5 × 1010 1 mole−1 sec−1 (recombination) and kD = 1.5 × 107 sec−1 (dissociation). The association effect, which shows a strong dependence of the relaxation time on the field strength, is discussed with regard to possible field effects, including a hypothetical structure field effect. A kinetic model is suggested for the succeeding reaction. The slow dissociation effect indicates the equilibration between monomers and micelles. The dependence of the time constant on the total detergent concentration has a slope d(1τ)dc = 1.5 × 107 1 mole−1 sec−1 and an intercept (1/τ)c=0= −4.2 × 103 sec−1. These results are discussed on the basis of two kinetic models, which assume a monodisperse [Krescheck, G. C., et al., J. Amer. Chem. Soc.88, 246 (1966)] or polydisperse [Sams, P. J., Wyn-Jones, E., and Rassing, J., Chem. Phys. Letters13, 233 (1972)] micelle population.
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